Steam bending of single ply planks softens the wood so it can be more easily formed. So how does microwaving the wood plank work? I ask because PEARL used a microwave process to create their single ply shells of the early 1990's. Microwaving "excites" the water molecules in an object to create heat, but moisture is lost in the process. I guess if the wood was moist enough the loss could be tolerated and the result is wood with a hot water content/steam. Leave it to the Japanese!
Sumo Dude